Green Party officials say they will submit nominating petitions today containing more than enough signatures to secure ballot spots for their candidates for U.S. Senate and governor.

That development has the potential to unsettle the dynamics of a Senate race in which Democratic state Treasurer Bob Casey has held a steady, double-digit polling lead over Republican U.S. Sen. Rick Santorum.

Among the perceived assets of Mr. Casey's challenge to the incumbent are his relatively conservative positions on social issues such as abortion and gun control, neutralizing volatile issues that have helped Mr. Santorum appeal to more conservative Democrats in past elections.

Mr. Casey's moderate profile, however, has estranged him from some liberal Democrats. Should Carl Romanelli, the Green Party's Senate nominee, survive potential challenges to the petitions he will submit today, those Democrats would suddenly have the option of voting for a pro-choice candidate in November.

Mr. Casey easily brushed aside two pro-choice competitors for the Democratic nomination in the May primary. But if Mr. Santorum were to close the gap with Mr. Casey, even a minimal level of support for Mr. Romanelli could conceivably be enough to turn the race toward the Republican.

Campaigning in Green Tree yesterday, Mr. Santorum freely acknowledged his campaign's cooperation with the Green Party candidate with whom he has little ideological affinity. In answer to a question, Mr. Santorum said he's encouraged his campaign staff and other supporters to assist in the petition drive.

"It's no surprise to anyone that when you're an incumbent, having more people on the ballot benefits [you]," he said. "This is politics."

The Casey campaign charged yesterday that the Green Party petition drive had been fueled by Republican money that flouted the Federal Election Commission's contribution ceilings.

In a news release, Democrats charged that the Green Party had received $66,000 from traditional GOP contributors and used that money to collect signatures for the Romanelli petitions. Larry Smar, a spokesman for Mr. Casey, argued that FEC regulations should have limited the party's in-kind contribution to the Romanelli campaign to $5,000.

Asked if the Casey campaign planned to challenge the Romanelli petitions, Mr. Smar said, "We'll cross that bridge if we come to it."

In response to a question on whether the Romanelli candidacy posed a problem for the challenger, Mr. Smar said, "I don't know. Santorum thinks it would be a problem; otherwise he wouldn't be throwing his support behind him. Rick Santorum and his allies are trying to steal this election."

Virginia Davis, the Santorum campaign press secretary, defended the efforts on behalf of the prospective Green Party opponent.

"Our campaign has been transparent in encouraging Republicans, Democrats and independents to help in this effort," she said. "I think the bigger question here is: Why is Bob Casey going to such extremes to silence another voice in the Democratic process?"

The Santorum campaign's exertions on behalf of the Democratic process haven't extended to other potential third-party candidates, however. Carl Edwards is the nominee of the Constitution Party, a conservative group whose appeal overlaps Mr. Santorum's, just as the Green Party's does Mr. Casey's. Tom Martin, a Libertarian Party candidate, has also been seeking to meet the towering signature threshold for independent candidates.

Mr. Santorum and his allies have been silent on these potential candidacies.

Under state law, Mr. Romanelli or any other third-party candidate seeking a spot on the statewide ballot had until today to submit 67,070 signatures from registered voters. That figure equals 2 percent of the total of the highest vote-getter in the last statewide election. In 2004, that was Mr. Casey.

Independent candidates have long argued that Pennsylvania's signature requirements amount to an unfair advantage for the two major parties. A federal judge in Harrisburg rejected a lawsuit challenging the rule's constitutionality.

The third-party plaintiffs have appealed that decision although it is not known whether the 3rd U.S. Circuit Court of Appeals will rule on it in time to have an impact on the number of names on the November ballot.

Marakay J. Rogers, the Green Party nominee for governor, hopes to submit enough signatures to win a spot against Gov. Ed Rendell and Republican challenger Lynn Swann. But another relatively high profile, third-party candidate for governor, Russ Diamond, all but conceded in an interview with The Associated Press that he would fall well short in his signature quest.

The prospect of a third-party candidate in the governor's race, however, does not appear to have the same potential tactical impact as in the Senate contest. Mr. Rendell is pro-choice, so he is less vulnerable than Mr. Casey to Democratic defections prompted by the abortion issue.

And as the incumbent, Mr. Rendell, already the favorite against Mr. Swann, would stand to benefit from the "more-the-merrier" dynamic alluded to by Mr. Santorum.